FIGURE 2.6 Reference global primary energy consumption projections from the models used in the EMF22 study. Note that all estimates project considerable growth in energy production over the course of the century. SOURCE: Adapted from Clarke et al. (2009).

2050 range between 800 and 1,500 ppm⁵ CO₂-eq, in contrast to today’s concentrations of roughly 440 ppm CO₂-eq.)

Although the high-income (OECD) countries are currently the largest contributors to cumulative GHG emissions, emissions from rapidly growing low- and middle-income countries (e.g., Brazil, China, and India) are projected to grow more quickly than those of high-income countries. Figure 2.8 shows historical and projected contributions to global emissions out to 2100 from several sources. In all the projections, the balance of cumulative GHG contributions shifts from the high-income to the low- and middle-income countries through 2050; in second half of the 21st century, the low- and middle-